1. Field of the Invention
The present invention relates to a machine for fracture separating a connecting rod and a method for fracture separating a connecting rod using the machine. More particularly, it relates to a machine and a method for fracture separating a connecting rod, in which a half-split type mandrel is fitted into an opening of a large end portion of a connecting rod to expand the opposed half portions of the mandrel and thus separate said opening portion, and the large end portion of said connecting rod is thereby fracture separated into a cap portion and a rod portion along embrittled portions, which are provided in advance on the inner surface of the opening portion.
2. Related Arts
A connecting rod (hereinafter referred to as a con-rod) is to connect between the crankshaft and the piston head of an engine. The con-rod has a bearing portion or an opening of the large end portion (hereinafter referred to as a large end bearing) and another bearing portion or a small end portion (hereinafter referred to as a small end bearing). The large end bearing supports a journal of said crankshaft, while the small end bearing supports the piston pin. The piston pin is allowed to penetrate the small end bearing and both ends thereof are supported by the bearings of the piston head. On the other hand, the large end bearing is separated into halves, or rod and cap portions, at a predetermined diametric position to encircle a journal of the crankshaft. After that, the rod and cap portions are bolted securely to each other to support said journal.
There is an FS (Fracture Separation) technique available for separating the large end portion of the con-rod into halves or rod and cap portions. FIG. 1 is an explanatory view illustrating the fracture of the con-rod by a related FS technique. As shown in FIG. 1, along the axial direction, provided are in advance embrittled portions, for example, notch grooves 2a, 2a subject to a concentrated stress at predetermined diametrical positions of the large end bearing 2 of the integral preform con-rod 1. Then, the large end bearing 2 is mated with the half portions 4a, 4b of a half-split type mandrel 4 which are separated into halves at the positions corresponding to the notch grooves 2a. Thereafter, a wedge 5 is inserted in between the mandrel half portions 4a, 4b to provide a separating force therebetween, thereby fracture separating a large end portion 1a starting from the notch grooves 2a, 2a. The present fracture separation method is to thus fracture separate the con-rod 1 into a rod portion 1A and a cap portion 1B.
Now, a con-rod fracture machine is considered which causes fracture separation of the large end portion 1a of the con-rod into the rod portion 1A and the cap portion 1B in accordance with the aforementioned FS technique. In the machine, any one of the mandrel half portions 4a, 4b, for example, the mandrel half portion 4a is fixed to a support member 7, whereas the other mandrel half portion 4b is fixed to a support member 8 which is slidable apart from the mandrel half portion 4a. On the support member 8, there is provided a clamp member 9 for clamping the small end portion 1b of the con-rod 1. Also provided thereon are clamp members 10, 10 and 11, 11 for clamping both right and left shoulder portions of and both sides of the rod portion 1A of the large end portion 1a. Moreover, provided on the support member 7 are clamp members 12, 12 for clamping both right and left shoulder portions of the cap portion 1B.
Upon fracture of the large end portion 1a, each of the clamp members 9-12 first clamps securely the con-rod 1 at the front, back, right, and left thereof. Subsequently, the wedge 5 is used to expand the mandrel half portions 4a, 4b and thus fracture separate the large end portion 1a, or the large end bearing 2 along the notch grooves 2a, 2a. As the large end portion 1a is fracture separated, the support member 8 moves in the direction shown by the arrow to cause the con-rod 1 to be separated into halves, or the rod portion 1A and the cap portion 1B.
However, the aforementioned con-rod fracture machine clamps both the right and left shoulder portions of the rod portion 1A of the con-rod 1 or the vicinity thereof, both the right and left side portions, the large end portion 1a, and the small end portion 1b. This clamping arrangement readily causes the aforementioned con-rod fracture machine to provide chipping upon fracture and a bad surface property (surface roughness) for the fracture planes. In addition, movement of only one half of the mandrel or the mandrel half portion 4b (one-half movable mandrel) will not allow the large end bearing 2 to be uniformly loaded for expansion. Therefore, such a problem is introduced that the con-rod fractured by the aforementioned con-rod fracture machine is provided with a large amount of strain and an unstable shape of split planes.
The present invention was developed in view of the aforementioned problems. An object of the present invention is to provide a con-rod fracture machine which eliminates chipping upon fracture and provides stable properties for fracture surfaces. Another object is to provide a method for fracturing a con-rod using the machine.
To achieve the aforementioned object, the con-rod fracture machine according to the present invention comprises first and second support members for horizontally supporting a large end portion and a rod portion of a con-rod. The first and second support members are arranged movably apart from each other on a base of a pallet for placing thereon the con-rod to be fractured. The machine also comprises a half-split type mandrel, vertically provided on said first and second support members, comprising two mandrel half portions with each outer peripheral surface thereof fitted into and in contact with an inner surface of an opening of said large end portion. Moreover, the machine comprises a wedge, with tapered surfaces in contact with opposite edge surfaces of said mandrel half portions, for separating said mandrel half portions uniformly apart from each other. The machine also comprises an actuator for applying a load to said wedge. Furthermore, the machine comprises control means for applying an initial load to said actuator to bring each of said mandrel half portions into contact with said inner surface of the opening and thereafter applying a fracture load to instantaneously fracture said opening.
On the other hand, the method for fracture separating a con-rod according to the present invention comprises a step of placing a con-rod to be fractured on a pallet. The method further comprises a step of holding said con-rod by supporting a large end portion and a rod portion of said con-rod by means of first and second support members arranged on a base of said pallet movably apart from each other. Furthermore, the method comprises a step of bringing each outer peripheral surface of a half-split type mandrel mateably into contact with the inner surface of an opening of said large end portion. Here, the half-split type mandrel is vertically provided on said first and second support members and comprises two mandrel half portions. The method also comprises a step of applying an initial load to the inner surface of said opening using a wedge to bring each of said mandrel half portions into contact with the inner surface of said opening. The wedge has tapered surfaces in contact with opposite edge surfaces of said mandrel half portions. Finally, the method comprises a step of fracturing said opening instantaneously by applying a fracture load to the inner surface of said opening using said wedge.
As described above, the half-split type mandrel is mated with the opening of the large end portion of the con-rod. Then, the opposite mandrel half portions are expanded to expand said opening in order to fracture separate said con-rod into cap and rod portions along embrittled portions provided in advance on the inner surface of said opening.
Said first support member preferably comprises a pressing member for pressing both shoulder portions of the cap portion of the con-rod against said mandrel half portions, respectively. Moreover, said second support member preferably comprises an engagement member for holding the small end portion of said con-rod.
When the control means apply the initial load to the actuator, the actuator extends to cause the wedge to be lowered and inserted in between the opposed mandrel half portions. The mandrel half portions are expanded with the wedge apart from each other to allow each of the outer peripheral surfaces thereof to be positively brought into contact with the inner peripheral surface of the opening of the large end portion. Then, upon application of the fracture load to the actuator, the wedge expands instantaneously the opposed mandrel half portions apart from each other in conjunction with the first and second support members, thereby fracture separating the opening instantaneously. The wedge has tapered surfaces to be in contact with the mandrel half portions, thereby separating uniformly the mandrel half portions apart from each other. As described above, the fracture load is instantaneously applied and the mandrel half portions are uniformly separated apart from each other. This thereby prevents chipping and provides a stable property for the fracture surfaces (surface roughness), thus making it possible to provide stabilized shapes for the split planes. In addition, it is made possible to reduce the amount of strain produced in the opening.
When the opening is fracture separated, any one of the embrittled portions formed on the large end bearing of the con-rod can be fractured first (first fracture) and then the other portion is fractured after a very short time lag (second fracture). The pressing member of the first support member presses both shoulder portions of the cap portion of the con-rod when fractured to hold the cap portion in cooperation with the mandrel half portions. The second support member allows the engagement member to engage the small end portion of the con-rod or engages the rod portion at the farthermost position from the mandrel half portions, thereby well preventing sideward displacement of the rod portion. This makes it possible to provide a stabilized property for the fracture surfaces subjected to the second fracture caused by said time lag.
The con-rod is preferably fractured using a con-rod fracture machine in which the engagement member of the second support member has, on a front-end portion thereof, a notch opened in the shape of a letter V.
It is possible to prevent displacement of the con-rod by holding, with the notch opened in the shape of a letter V, the small end portion of the con-rod when fractured. The shape of the fracture surfaces of the con-rod can thereby be stabilized.
The con-rod is preferably fractured using a con-rod fracture machine in which each of the mandrel half portions is allowed to contact with the inner surface of the large end bearing at three points of the outer peripheral surface of each of the mandrel half portions.
The three-point support structure of the mandrel makes it possible to bring the mandrel half portions into good contact with the inner surface of the large end bearing. This is particularly useful when the unfinished (e.g., as forged) large end bearing of the con-rod is fractured (cracked).
The con-rod is preferably fractured using a con-rod fracture machine comprising an actuator and a cylinder for moving the wedge toward the mandrel. Here, the actuator comprises an accumulator for accumulating a high-pressure working fluid and a valve for instantaneously supplying the high-pressure working fluid from the accumulator to the cylinder.
The accumulator is employed to apply the fracture load to the large end bearing instantaneously. This makes it thereby possible to provide a stable property for the fracture surfaces (surface roughness) and provide stabilized shapes for the split planes.